to produce a graph, stored in out.dot, and the adjacency matrix of the graph,
stored in out.map, run:

stack build
stack exec -- store-graph-exe ./store/

The blog post data is included in the data folder. Unfortunately I
didn't save the exact nixpkgs revision that I used to generate it. If you rerun
the program, you might get slightly different results because it will be
generated for the nixpkgs revision that is saved in
nixpkgs.nix.